Telephone-exchange system.



N.G.SC-HELLENGER. l

TELEPHONE EXCHANGE SYSTEM.

IAPPLIOATION FILED P11111 1 1901.-

Patented May 9,1911.

. STAZQEQATE NEWTON c. scnsrnnnenm or omcaso,

Imus, TQI STEOMBERG-CARLSON TELEPHONE MANUFACTURING COMPANY, 01 iaocnns'lfE NEW Yemen conron-A'rroir on NEW ronx.

I To' all it may alum Be 'it known that I, i nw'ron C. ScriEL nnxonn, aicitizen oft-he United States, resid- "ing at Ghicago,'in .the county ofCook'and State of Illinois, have invented a certainnew and useful 'Improvemehtin Telephone-Exchange Systems, of which the following is a j full, clear, -concise,and exact description,

reference. being bad to' the accompanying drawings, forming a' part of this specification; o a

My inventionrelates to telephone exchange systems, and has for its object the provision of improved supervisory and clearing-outsignahng apparatus,

an improved supervisory signaling apparatus, which may be'employed in connectionwith the cord circuitshaving but tw'ostrands.

In accordance with-my invention," I employ two indicators, preferably in'the form ofincandescent lamps, which, through the agency'ofelectro-magnetic apparatus inter- 'vening between .-the same and the subscribeisgstations,arehadapted to indicate the condition ofuse 'of- 'thefca-lling and called subscribers lines, respectively.

'In practicing my invention, I employ two 'relays'associated with each supervisory or clearing out signal. A relayassociated with each supervisoryslgnal is operated through J the. agencyof the-switch hook a-t'the correspon ing station vwhen the said switch hook r j -suPPOrtsthe receiver at its station to effect as switch hook is relieved of'the-weight' of the the operation of said signal. When the receiver, the second relay is o erated'to 'restore the 'si al. 'I preferab yemploy at each subscri rs stationza grounded bell of low resistance, say 200 ohms, WhlCll, when included in Cil'Cllllx' with the corresponding telephone switch book, when thelatter is depressed by the supported receiver serves to V with-each supervisory signal is connected in br1dge of ti e cord'circuit and preferably in the samebridge and inserlcs connect-Ion with-its companion relay, sothat when the Specification'bt Letters Batent. a lication filed February 14,1901. Ser ia1No.-47 21 8.

One object of my invention is to provide' 'rnLErHonE-ExcHANeE' sYs'rEM;

' telephone switch is elevated," circuit may be NT-O F QE ILLINOIS, ASSIGNOR, BY' MESNEPASSIGN- Patented n y-e; 1'9 f closed throughthe said relays and the com-'..

anon battery'in' circuitftherewith, by Which" arrangement the first relay has its condition.

of operation unchanged, wl 'Ie the second;

relay has its condition of use change'dato restore the associated supervisorysignahto,

its normal condition. 'The second relay may be employed eitherto shunt the associated] supervisory signal .or to open the circuit iii;

which it is included; or the supervisory sigi nal may beotherwise restored through the a Y agency of the second delay.- By these means I I am enabled to retain the two sets of two whereby the requisite impedance-maybe se-l of the supervisory signals. may be secured through t e agency of these relays without vices.

y illustrating two embodiments thereof, in whichr Fi'gure' 1 is a diagrammatic view "illus-- 'trating telephone substations united for conversation through a cord circuit constructed 1 relaysfea-ch in bridge of the cord circuitcured, while at the same time the operation in accordance with the invention; and Fig.

2 a diagrammatic illustration of a modifies-f tion of the cord circuit illustrated in Fig.1, Llke parts are indicated by sim lar char-:- acters of reference in both views.

The apparatus at the substations-1O and constitutes the preferred apparatus used J in practicing my invention.

A battery transmitter a, with its primary coil I) an receiver 0, is Illustrated ateach of 7 these 1;

stations, a secondary coil. being included in this instance in a localcircuit with thetele phone receiver there:-1t,.while the primary coil in circuit' with the transmitter is placed in circuit with both'limbs ofthe corresponding telephone .line upon the removal of the receiver from its spring switch hook. The transmitterprimary winding of the induc, tion coil atthe station 10' is thus shown in series with the telephone linefthe telephone I receiver at this station being removed from its hook. This station 1nay, 'f0r example, illustrate the station of acalhng subscrlber.

The transmitter circuit at station 90, which may illustrate a called subscriber s'station,

is open, the receiver at said station being- -'lines'extend to spring jacks gfg attheexupon itsho oli." There is also 'provided' at each substation a call bell (1, preferably responsive to alternating current, which I IQ'fGItO' include-in a grounded branch that l is closed when the telephone receiver at that station is upon its hook. Each call bell d is preferably of low' resistance, s a 2000111113.;

Other substation apparatus may 1e equipped, however, without departing from the spirit of 'my invention; Metallic circuit telephone lines extend from the substations to an exchange, thelimbs e and f of which metallic change. -A battery 7.: is connected in bridge between the-sides of idle telephone lines. The limb f of :each line-terminates in a spring lever. I normally resting against a contact constituting a terminal of a line in-' dicator, m, the other terminal of the line indicator being connected with one termiu'al of the said battery, while the remaining terminal of the battery is connected with the back contact of the, remaining spring lover of the spring, jack;

A subscriber, in initiating 'a call, closes circuit of the battery A: through the line in;

dicator, the springs and back-contacts of the spring jack. Theoperator, in response to this signal, inserts the answering plug it within the jackof the calling subscriber and by means of a well known listeningkey includes her telephone set o in circuit/with thei calling subscribers telephone set, Ascertaining that this subscriberdesires communication with subscriber No. 90,- she inserts the connecting plug p, the mate to plug n, within the line jack of the called subscriber, and by means of a well known ringing key includes the grounded generator g in circuitwith the tip strand of the connecting plug, the limb e of a called 'subscribers telephone line and his grounded bell d. The tip and sleeve strands of the cord circuitinclude condensers r, r series with'eacli other and in; shunt oflthe condenser r. The relays t, t are correspond efl'ected y its connection with the relays,

owing to the fact that condensers r and r prevent passage of straiglit=current across .the cord circuit where these condensers arelocated. In order to prevent voi'ce currents from being shunted through the connections including the common batte u, the shunt conductors, including 'there ayss, s and 1 t, t. are provided with" sufficient mpedance or .inductance. This inductance s prefer- Relays s, s arein'clud'ed in' ably'diieitothe windings 5f't1'iie15' The I advantages of such av method of "distributing battery current to the transmitters atthe subscribers stationsla're well' known tolthose skilled the art. The relays :8 ,8 each' preferably ,has its armature provided 'withan alternate contact that constitutes one ter- ,minal of a localzcircuit, the other terminal of the said local-circuit preferably eompris-. ing the 'arinatii're This local circuit includes a suitable form ,ofsupervisory signal,

preferably in tl'ie'form of an incandescent amp '0' and also the common battery :u. The

said common battery may be, for example, a twenty-four'volt battery, while' the indica-' tois 'v, v may be-twelve voltflamps. To cutthe' currentincluding the common battery and indicators down, 'I include resistance coils 1'0, to in the localcircuits that may be of, say,-eighty-f oiir ohms Each of the relayss, a, t, t may be wound to, say, eightyfive ohms. T e common battery u is ground ed at the point where it is connected .be- .tween'the relays. tfand t, sothat when the tel'eplioneswitoh hooks arefdepressed b the receiver's placed thereon, ,cir'cuit-is c osed through the relays s, s','or-either of thesev relays, as the case may 'be, -according to. the

position of the-"switch hooks, to" close the "said local circuit, or'bot'hof them, and effect a c'orre'spondin /op'eration oithe. supervil herelays t,-t" may, as illus-.

sory-si als. trated in Fig. l, have their armatures and alternate contacts included in shunt connections about the superv sory signals, IGSlSt ance' coilsfw, a2, wound preferaly ?to forty ohms,- being included in these .shunt' -connec- 'tions. W'he'n'th'e telephone switch hooks are. elevated, these relays t, t are energized and the saidishunt circuits are established about the'super-viso signals. r The, genera operation of the preferred form of my invention is substant ally as follows: Upon'insertioiiof the answering plug Iinvthe calling 's ibscribers jack,',a practically rinanently closed circuit is formed which includes the'winding of oneof :the relays by means of which inclusion the; said-relay serves to placej'the supervisory lamp associatedtbere'withi in" an operative condition; that "is, it" serves" to place: the" signal lamp in a closed "circuit ,with a source of current. The'said closed circIi-itiiicluding the relay is established or maintained irrespective .of the-operative osition-Iof the switchhoekat the calling su scribers',s tation.- It will seen that when the receiver is upon the pressed, current will flow-'from-the battery a through the relay- 8, tlielimb e. of the cir-.

ound,' .one ter'-,

grounded; -When the receiver-"is v reti' 'o've from the cuit, the signal'bell dfiominal oi the battery i switch hook, and the said switch hookisdeswitch ho k; so that the-switch hook is'in its raised condition, it -'wil'l; be seen that current;

"subscribers circuit, relay 1, back to the other pole of the battery 2!.

still flows through the relay a, circuit I station. Vhen the called subscriber re through the sa ine being traced from; one ternii ial of the battery '11 through the'relayy s, limb e of the circuit, switch hook, secondary coil 7),- transniitter a, limb f of the It is of course possible to provide other circuit, connections than thosespecifically shown herein for establishing a closed circuit tlilOQ h a relay, and I do not wish to liinit iiiysc f to a closedcirciiit in which the the normal contacts'of the relays t, t and station apparatus takes place.

subscribers line a part.

A closed circuit through the relay 8, after being once established, is, as has been stated. maintained irrespective of the operative position of substation apparatus, and for this reason other means should be 'n'ovided'to render the supervisory signal and the switch hook form inert and to effect a change in the operative.

condition of the supervisory signal when a change in the operative condition of sub- This said means is preferably in the form of the second relay t which is directly under the con trol. of substation apparatus. The specific means employed, in this instance, preferably has a shunt circuit including the resistance a: that is shunted about the supervisory signal when the same is to be rendered inert.

The arrangement illustrated in Fig. 2 may In this ar- 8 are preferably in the same circuit relation with the cord circuit as illustrated in Fig. 1, as are 'alsotherelays t,t. In order to cut out the supervisory signalsv', '01, they are illustrated in Fig. '2 as being included in normall openlocal circuit conductors in which con uctors the engaging arniatures areincluded. When the relays s and t is not grounded batteryubeingalone included in grountled bell the relays t, t, ill'ustratedin Fig. erated, a circuit through signals 1;,

2, are opthe supervisory q) is opened, so that these signals are restored to the norma-lcondition, where-- by-the'same result is secured as in shunting the said signals. Circu t including the su pervisory relays sand #18 at once established upon the insertion of the answeringplug Within the calling.subscribers-jaek, as

the said calling-subscriber has his telephone- The corresponding.

removed from its hook.

the cord circu t is called subscribers supervisory signal vupon the right of the cord circuit, however, is at once actuated, because initially the circuit including the bridge connection, including established, the

a. grounded circuit with the relay s and/the (Z at the called subscribers' It will circuit, a condenser but v v y Having thus described-my invention, I

Patent from substations ,toan exch sponds by removing his telephone from its ing the relays s and t and the battery u. is established; so that although thecircuit through the corresponding signal "0 may be partially completed by the relay 8', it is either shunted because of the attraction, of the armature of relay t, in the arrangement illustrated in Fig. 1, or is cut out of circuit, owing'to the attraction of the corresponding relay illustrated in Fig. 2. \Vhen the called subscribers signal '0 is thus restored to its normal condition, the operator knows that he has responded and that the subscribers are in conversation. When both subscribers restore their receivers the relays s and s'- are alone included in grounded circuits with the battery u and the call bells (Z, d, the relays t, if being out of circuit,.so that the supervisory signals 4:,- o are both actuated or caused to glow, positively indicating'to the operator that both subscribers have finished conversation, and thatdisconnection between the same may be effected. Obviously, when'either subscriber restores his receiver, Whether the other does ornotj, the supervisorysignal corresponding to his line is caused to operate. The relays-at each end of the cord circuit. are preferably included 111- series with respect to eachvother in the same bridge strand across the cord'circuit. I' do not wish to be limited however,to the particular arrangement of the bridge or branchconductors connected with theside ,of the cord circuit or to the relative arrange-' ;ment of the relays at each end of the cord circuit, as other includin coming t means may be'em loyed for: the relas in circuit and for overeimpe aiice due thereto. be observed that I have provided .tWO-PEII'S, of relays inbridge-of the cord I being included in each strand of thecord circuit between the connections of the relays. rent is also grounded, whereby in one co'ndition of use of the substation apparatus one relay will serve to place the corresponding supervisory signal in one-condition of use and both relays of in multiple,.'co6perating, will place the said supervisory signal in another condition of use.

Iris obvious that other modifications of myinventionmay be' devised,..without de- 120 7 parting from the therefore, wish to be limited to the precise f disclosure of the invention herein set .forth;

claim as new and desire to secure by Letters In a tele hone exchange system, the combination with vtelephone ine's extendin ange, each o? 1 ZThe sourceof cureach pair included spirit thereof, and I do not, Y I

- grounded common battery having one termiswitch hooks at the subscribers stations are.

adapted to operate each of said relays independently of the other toactuate the cor responding indicator, a second supervisory relay associated with each supervisory signal adapted through the agency of the switch hooks to restore the supervisory signals each independently of the other, and means whereby the latter relays are both actuated independently of each other by the said switch hooks, substantially as described.

2. In a telephone exchange system, the combination with telephone lines extending from subscribers stations to an exchange, of a grounded signal bell at each subscribers station, a switch hook at each subscribers station adapted to connect the grounded bell with the side of the telephone line to which the switch hook is connected, a grounded common battery at the exchange, supervisory relays having terminals connected to the same side of the telephone line, a condenser between the said terminals, said nal included between the remaining teiininals of the said supervisory relays, whereby the said battery may be included in circuit with each supervisory relay independently of the other through the agency of the corresponding switch hooks at the subscribers stations, a supervisory signal associated with each relay and adapted to be operated thereby, two additional supervisory relays having terminals of each connected together, the remaining terminal of the said common battery being connected to both the said terminals while the remaining terminals of the additional supervisory relays are connected with the remaining limbs of the telephone lines, a condenser included between the latter terminals of the additional supervisory relays, and means whereby when thesaid additional supervisory relays are both or either included in circuit-with both limbs of the telephone line upon the release of the corresponding telephone switch hooks the supervisory signals are restored, substantially as described.

8. The combination with telephone lines extending from subscribers stations to an exchange, of a cord circuit at the exchange provided with two strands for forming connections between two telephone lines, a conlenser in each of said strands, two supervisory signals, onefor eachsubstation, four relays for the cord circuit, two in shunt of one condenser and two in shunt of the other,

a source of current, and a conductor having connection between the relays included in shunt of each condenser, whereby the relays corresponding to one end and the other end of the cord circuit may be operated through the agency of the corresponding switch hooks at the connected subscribers stations,

the armatures of the relays at each end of the cord circuit having contacts and con nections for governing the operation of the corresponding supervisory signal jointly, substantially as described.

4:. The combination with telephone lines extending from subscribers stations to an exchange, of a cord circuit at the exchange provided with-two strands for forming connections between two telephone lines, a pair of relays corresponding to each end of the cord circuit and included in bridge thereof, a source of current for inclusion in circuit with each of said pairs of relays, and a supervisory signal for each pair of relays and jointly controlled thereby through the agency of the substation apparatus, substantially as described.

5. The combination with telephone lines extending from subscribers stations to an exchange, of a cord circuit at the exchange provided with two strands for forming connections between two telephone lines, a pair of relays corresponding to each end of the cord circuit and included in bridge thereof, a source of current for inclusion in circuit with each of said pairs of relays, a supervisory signal for each pair of relays and jointly controlled thereby through the a gcncy of the substation apparatus, and a condenser included in each cord strand between the connections of the relays therewith, substantially as described.

6. The combination with telephone lines extending from subscribers stations to an exchange, of a cord circuit at the exchange provided with two strands for forming connections between two telephone lines, a condenser in each of said strands, two supervisory signals, one for each substation, four relays for the cord circuit, two in shunt of one condenser and two in shunt of the other, a source of current, a conductor having connection between the relays included in shunt of each condenser, whereby the relays coi' responding to one end and the other end of the cord circuitmay be operated through the agency of the corresponding switch hooks at the connected subscribers stations, the ar matures of the relays at each end of the cord. circuit having contacts and connections for governing the operation of the corresponding superviso y signals jointly, the said 4 source of current being grounded, and a ground-connection Ior each telephone line to include the said source of current in a grounded circuit, one relay of each pair that is controlled by a subscribers station apparatus beingincluded in the corresponding grounded clrcu t containing the ground connectlonand the ground at the source of curin one condition of use and both relays co: operating place the supervisory signal in another condltion of use, substantially as described. f

T. The combination-w th telephone lines extending fromsubscribers: stations to an exchange, of a cord circuit at the exchange provided with two strands for forming connections between two telephone lines, a pair of relays corresponding to each end of the cord circuit and included in bridge thereof, a source of current for inclusion in circuit with each .of said pairs of relays,ca supervisory signal for each pair of relays and ointly controlled thereby through the agency of the substation apparatus, the said source of current being grounded, and a ground connection for each telephone line to include the said source of current in a grounded circuit, one' relay of each pair that is controlled by'a subscribersstation apparatus being included in the corresponding grounded cirfl cuit containing the ground connection and the ground at the source of current, whereby one relay of each of these latter pairs mayplace the supervisory signal-in one condition of use and both relays cooperating lace the supervisory signal in another con ition of use, substantially as described. p

8. The combination with telephone lines extending from subscribers stations to, an

exchange, of a cord circuit at the exchange provided with two strands for forming connections between two telephone lines,ia pair of relays corresponding to each end of the cord circuit and included in bridge thereof,

a source of current for inclusion in circuit with each of saidpairs of relays, a supervisory signal for each pair of relays and jointly controlled thereby through the agency of the substation apparatus, a condenser included ineach cord strand-betweenthe connections of the relays therewith, the said source of current being grounded, and a ground connection for each telephone line to include the said source of current. in a grounded circuit, one relay of. each pair that-1s controlled by a subscribers station apparatus being 1n- .cluded in the corresponding grounded circuit containing the gr'ound connection and i the ground at the source-of current, whereby one relayof each of these latter pairs may place the supervisory signal inone condition of use and both relays cooperating place the supervisory si dition ofuse,'substantia ly as described,

.9. The combination with a telephone substation provided witha receiver, a trans mitter and a switch hook,:of a'magnet adapted for inclusion in the circ uit',a branch con al in another conductor connected wit-l1 the cord circuit including the said magnet, a source of current 5 adapted tor inclusion in circuit with the rent, whereby one relay of each of these lat-y E ter pairs may place the supervisory signal magnet winding through the agency of the switch hook, the armature of the said magnet being provided with a contact and engaged thereby upon a change in the 0peraj tive condition of the said magnet, a supplemental electromagnet, means for effecting its inclusion in circuit with its source of current and withthe switch hook at the substation independently of the aforesaid electromagnet, and a signal cooperatively asso-' ciated with said magnets, its circuit including the aforesaid armature and its contact, substantially as described.

10. The combination with telephone lines extending from subscribers. stations to an exchange, of a cord circuit atthe exchange provided with two strands for forming connections between two telephone lines, a pair nections between twotelephone lines, a .pair

of relays corresponding to each end of the cord circuit and included in bridge'thereof, a source of. current for inclusion in circuitwith each of said pairs of relays, a supervisdr signal'for each pair of relays and joint y controlled thereby, switching apparadius for controlling the'operation of the relays, and a condenser included in each cord strand between the connections of the relays therewith, substantially as described,

. 12. Thecombination with telephone lines extending from subscribers stations to an exchange, of a cord circuit at the exchange provided with two strands for forming connections between two-telephone lines, a pair of relays corresponding to each end of the cord'circuit and included in bridge'thereof, a source of current for inclusion in circuit with each of said pairs ofrelays, a. supervisory signal for each .pair relays-and jointly, cont-rolled thereby, the said source of current vbeing grounded, and aground connection for each telephone line to include the saidsource' of current in a grounded circuit, one relay of each pair being included in the corresponding grounded circuit containing-the ground connection and the'ground at thesource of current, whereby one-relay of each of theselatter pairs may place the supervisory signal in one condition of use and-both relays cooperating place the. super isovisory signal in another condition of use,

nism for controlling the operation. ofv the relays, a condenser included inueach cord strand between the connctions'of the'relays therewith, the said; source of current being grounded, and a ground connection for each telephone line to include the said source of current in a grounded circuit, one relay: of each pair that is controlled by a subscribers station apparatus being included in the corresponding grounded circuit containing the ground connection-and the ground at the source of current, whereby one relay of each of these latter" pairs may place the supervisory signal in one condition of useand both relays cooperating place the supervi'sory signal in another condition of "use, substantially as described.

14. In a telephone system, the combination with subscribers lines extending from substations to an exchange, of a cord circuit at the exchange for interconnecting subscribers lines, a pair of relays corresponding to each end of the cord circuit and included in branch of the cord circuit, a supervisory signal associated with each pair of rel ys and jointly controlled thereby, means at the substation foreffecting operation of the corresponding signal through the agency of one of the said relays of the pair associated with said signal, and'means whereby the operative condition of the remaining relay of each pair is independent of the operative condition of substation apparatus, substantially as described.

15. In a telephone system, the combination with subscribers lines extending from substations to jacks at an exchange, of a cord circuit at the exchange for -interconnecting subscribers lines, a relay associated with said cord circuit, means including ajack and a cord circuit plug inserted in the jack for establishing a closed circuit through said relay, which is independent of the 0perative position of substation apparatus, a second relay also associated with said cord circuit, means whereby the latterrelay is re sponsive to changes in operative osition of substation apparatus, said relays eing serially included in a bridge across the said cord circuit, a source of current for energizing said relays, means formin a circuit for the flow of current from sai source in series a source of current for inclusion in circuitthrough said relays to the telephone substation and asupervisory signal ointly con trolled by said relays, substantially as described.

16. In a telephone system, the combination with subscribers lines extending from substations to jacks at an exchange, of a, cord circuit atthe exchange for intercornecting subscribers lines, a relay associated with saidcord circuit, means including a jack and a cord circuit plug inserted in the jack for establishing a closed circuit through said relay which is independent of the operative position of substation apparatus, a second relay also associated with said cord circuit, means whereby the latter relay is responsive to changes in operative position of substation apparatus,a source of current for energizing said relays, said relays and said source of current being serially included in a bridge across said cord circuit, and a supervisory signal jointly controlled by said relays, substantially as described. I

17, In a telephone system, the combination with subscribers lines extending from substations to jacks at an exchange, of a cord circuit at the exchange, supervisory signals located at the exchange corresponding to calling and called subscribers stations, relays at the exchange, one for each of the supervisory signals, means whereby changes in operative position of substation apparatus are adapted to operate each of said relays independently of the other, a second supervisory relay associated with each supervisory signal and included. with each of said aiore'said relays, in branch of the cord circuit, ineans including a jack and a cord circuit plug inserted in the jack for establishing a closed circuit through each of the latter relays, which circuit is independent of the operative position of substation apparatus,a source of current for said relays, and means whereby tl'ie'arinatures of the aforesaid relays are adapted jointly to control the supervisory signals associated therewith, substantially as described.

18. In a telephone system, the coinbina tion with subscribers? lines extending from substations to jacks at an exchange, of a cord circuit at the exchange, supervisory signals located at the'exchange corresponding to calling and called'subscribers stations. relays at the exchange, one for each of -the supervisory signals, means whereby changes in operative position of substation apparatus are adapted to operate each of said relays independently of the other, a seconisupervisory relay associated with each supervisory signal and included, with each of said aforesaid relays, in branch of the cord circuit, means including a jack and a cord cir cuit plug inserted in the jack for establishing a closed circuit through each of the latter relays, which is independent of the operative position of substation apparatus, a

source of current for said relays, means whereby the 'armatures of the last aforesaid relays are adapted when attracted to complete circuit through the corresponding supervisory signals, and means whereby the armatures of the first aforesaid relays when attracted are adapted to render said signals inert, substantially as described.

19. In a telephone system, the combination with subscribers lines extending from substations to jacks at an exchange, of a cord circuit at the exchange, supervisory signals located at the exchange corresponding to calling and called subscribers stations, re-

associated with a subscribers line, a source of current for said relays, and means wherelays at the exchange, one for each of the.

al and inc uded by the armatures of theaforesaid relays areadaptedv jointly to control -the superv1sory signals associated therewith, substantially as described.

20. The combination with-"telephone lines.

extending from substations to acksat an exchange, of a cord circuit at the exchange provided with two st-randsfor forming connections between subscriberslines, a pair of relays corresponding toieach end of the cord circuit and included in bridgethereof,

a source of current for energizing the said relays a su ervisorysignal for each pair of v relays'iand idintl y controlled thereby, switching mechanism atthesubstations forcontrolling the'operation of one ofeach pair of relays, means including a jack and a cord circuit plug inserted in the jack, whereby a closed circuit is established throu h the remaining relay of each pair whic istindcpendent of the operative position of the substation apparatus, and a condenser included in each cord strand between the connections of the relays therewith, substantially as de-' extending from-substations to jacks at-an exchange, of acord circuit at the exchange provided with two strands for forming connections between subscriber's lines, a pair-of electromagnets corresponding to each'end of the cord circuit and included in bridge thereof, a source oii current for energizing stantially as described.

additional electro-ma net .as described.-

the said elcctroniagnets and included in the same bridge therewith, a supervisory signal for each'palr of electromagnets, armatures and contacts for'said electromagnets, means whereby one of said armatures of each pair 7f; when actuated is adapted'to complete circuit through the supervisory signal associated therewith, means whereby the remaining armature when actuated is adapted to rendersaid signal inert, switching inechanism at the substations for controlling the operation of one of each pair of electromagnets, means including a jackand a cord circuit plug inserted in the jack, whereby a closed circuit is established through the remaining electromagnet of each pair which is independent of the operative position'of the substation apparatus, and a condenser included in each cord strand between the connections of the electromagnets therewith, substantially-as described. 1 I

22. The combination with a telephone line extending from a telephone substation to a jack at an exchange, said substation having a receiver, a transmitter and a swiich hook, of a magnet adapted for inclusic'gn in the circuit, a source of current adapted for inclusion in circuit with'the magnetwinding through the agency of the switch hook, a

supplemental electromagnet in a circuit coir ve ing all ofl'he current supplied to the su station transmitter, a cord circuit includin a plug for connectin a telephone line with another, a circuit including the supplemental electroinagnet substantially permanently closed by the plug of the cord circuit andthe jack engaging the said plug,

4 and a signal jointly controlled by said electromagnets, the said electi'onia' nets being included-1n branch of the cord pii'cuit, sub- 23. The combination with tel phone lines extending'from substations to jacks at an exchange, each of the said substations being provided with a receiver, a transmitter and a switch hook, of cord connecting apparatus terminating in answering 'and connecting plugs foruniting.subscribers for conversation, two electro-Inagnets one conresponding to each end of the cord circuit, trircuits for the said electro-magnets each substantially constantly closed by the corresponding cord circuit plug and jack engaging the same, an

included, with each of said aforcsai electromagnets, in branch of the cord circuit,fsaid additional electro-magnets bein included in circuits controlled by the switch hooks at the substations, and, two. indicators each jointly controlled by said electro magnets included in branch of the cord. circuit, substantially I 24.- The combination with telephbne extending from substations to aclts atf an exchange, each of the saidsubstationsbeing 130 provided with a receiver, a transmitter and a switch hook, of cord connecting apparatus terminating in answering and connecting plugs, for uniting subscribers for conversation, two clectromagncts, one corresponding to each end of the cord circuit, circuits for the said eleclromagncts each substantially constantly closed by the corresponding cord circuit plug and jack engaging the same, additional el'eetromagnets included in circuits controlled by the switch hooks at the substations, two indicators each jointly controlled by a magnet thus included in closed circuit and a corresponding magnet controlled by a switch hook, the said magnets being thus divided into pairs connected in branch of the cord circuit, each end of the cord circuit having a pair o -magnets associated therewitln'and a condenser in each cord strand between the connections of the electromagnets with the cord strands, substantially as described.

The "combination with telephone lines extending from substations to jacks at an exchange, each of the said, substations bemagnets being thus divided into pairs, each end of the cord circuit having a pair of magnets associated therewith, said pair of mag' nets'comprising one magnet included in closed circuit and the other included in a circuit, controlled by the corresponding switch hook, a condenser in each cord strand between the connections of the electromagnets with the cord strands, and bridge connections including the said electromagnets, substantially as described.

26. The combination with telephone lines extending from substations to jacks at an exchange, each of the said substations being provided with a receiver, a transmitter and a swltch book, of cord connecting apparatus terminating 1n answering and connecting plugs, for uniting subscribers for conversa-' tion, two electromagnets, one corresponding to each end of the cord circuit, circuits for the said electromagnets each substantially constantly closed by the corresponding cord circuit plug and jack engaging the same, additional electromagnets included incircuits controlled by the switch hooks at the subounce a stations, two indicators each jointly controlled by a magnet thus included in closed circuit and a corresponding magnetcontrolled by a switch hook, the said magnets being thus divided into pairs, each end of the cord circuit having a pair of magnets associated therewith, said pair of magnets comprising one magnet included in closed circuit and the other included in a circuit controlled by the corresponding switch hook, a condenser in each cord strand between the connections of the electromagnets with'thc cord strands, and two bridge connections across the cord circuit, each including a pair of-electromagnets.

27.111 a telephone exchange system, the combination with telephone lines extending from substations to an exchange, each of said substations being provided with a telephone switch hook for supporting the receiver therea't, of a common battery at the exchange, supervisory signals located at. the exchange corresponding to calling and called subscribers stat-ions, supervisory relays at the exchange, one for each of the supervisory signals bridge conductors including said relays, means whereby the switch hooks at the subscribers stations are adapted to operate each of said relays inde 'icndently of the other, a second supervisory relay associated with each supervisory signal for restoring the supervisory signals, bridge conductors for the second supervisory relays, and means whereby circuit through each ol said latter relays may-be closed independently of the other and independently of the operative position of the corresponding SWltCll hooks, substantially as described.

28, In a telephone exchange system, the combination with telephone lines extending from substations to an exchange, each of said substations being provided with a telephone switch hook for supporting the receiver thereat, of a common battery at the exchange, supervisory signals located at the exchange corresponding to calling and called subscribers stations, supervisory relays at the exchange, one for each of the supervisory signals, means whereby the switch hooks at. the subscribers stations are adapted to operate each of said relays independently of the other, a second supervisory relay associated with each supervisory signal for restoring the supervisory signals, bridge conductors for the second supervisory relays,

and means whereby circuit through each of said latter relays may be closed independently of the other and independently of the operative position of the corresponding switch hooks, substantially as described.

29. The combination with telephone lines extending from subscribers stations to an exchange, of a cord circuit at the exchange provided with two strands for forming connections between two telephone lines, a pair of relays corresponding to each end of the cord circuit and included in bridge thereof, a source. of current. for inclusion in circuit with each'of said pairs of relays, switching apparatus for controlling the operation of said relays, and a supervisory signaling as described.

30. In a telephone system, the combination with subscribers lines extending from sub stations to jacks at an exchange, of a cord circuit comprising two talking strands at the exchange for lnterconnecting subscribers lines, a relay'associated with said cordcircuit, means including a jack and a cord circuit plug inserted in the jack for establishing a closed circuit through said relay which is independent of the operative position of substation apparatus, a second relay also associated with said cord circuit, means whereby the latter relay is responsive to changes in the operative position of substation apparatus, said relays being included in a bridge across the telephone line, a source of current for energizing said relays, means closing a circuit for the flow of current in series through said relays and a supervisory slgnallng lamp in a local clrcuit serially 1n-' eluding contact-s controlled bysaid relays,

. substantially as described.

, 31'. In a telephone system, the combination with subscribers lines extending from substations to, jacks at an exchange, of a cord circuit at the exchange for intercon 'necting subscriberslines, a relay associated with said cord circuit, means including ajack and a cord circuit plug inserted in the jack for establishing a closed circuit through said relay which is independent of 'the operative position of substation apparatus,

\ said first/relay is in its attracted position I as described.

and when the armature of said second relay is in its unattracted position, substantially 32. In a telephone system, the combination of substations having grounded bells, a

central station having line connections with 1 said substations, a cord circuit with a condenser in each strand thereof, supervisory signals associated with the cord circuit,

means for supplying current bridged, across the cord circuit and connected with the cord described.

circuit strands at points each side of said condensers. impedancerelays interposed between said supply and said strands, and a connection for groundlng sald source of current supply, whereby both the bells at the substations and the supervisorysignals at the central station are brought into action by the closing of grounded circuits between the substations and the central station, substantially as described.

The combination with a telephone line, of a source of electricity and a pair of relays energized thereby adapted to be bridged between the limbs of the talking circuit thereof, a' switch at the substation and a switch at the central station for controlling the circuit through said relays, and a signal adapted to be controlled by the conjoint action of said relays, substantially as 34. The combination'with a pair of telephone lines, of an inductive device through which the same are adapted to be united for conversation, a charging source of electricity and a pair of relays adapted to be bridged between the two limbs of each of said lines,

one, pair of relays being individual to one of said lines and the other pair being individual to the other line, switches at the substations, and at the central station for controlling the circuit through said relays, and a signal controlled by the conjoint action of each pair of relays, substantially as described. j v

35. The combination with a metallic telephone line, of an operators plug and a cord circuit, a source ofcurrent and a pair of relays bridged across said circuit, a third conductor connected with .one pole of said source, one of said relays being adapted to be operated over the metallic line when the subscribers telephone is in use, and the other to be operated by current supplied from said source over a part of the line and said third conductor when the subscribers telephone is not in use and the operators plug is connected with the line, as described;

36. In a telephone system, the combination with a telephone line of a source of current and a relay bridged between the two limbs of the talking circuit thereof, a second relay at the central office deriving energizingcurrent from said bridged source of current over a path including a portion of oneside of the talking circuit individual to said line, a switch at the substation for controlling the circuit throughthe first relay, a switch at the central station for controllingthecirc-uit through both relays, and asignal controlled by the conjoint action of said relays, substantially-as described.

substantially 37. The combination with a metallic tele-Q phone line free from permanent grounds outside the central oflice, of a substation havin a telephone transmitter connected with sa d line, a third conductor, a pair of relays at the central ollicc, a source of current supplying current through said pair of relays to the substation transmitter, one of said' and one of said relays being adapted to be operated over a portion of said line and the third conductor, substantially as described.

39. Thecombination with a telephone line, of a charging source of electricity in a bridge between the limbs thereof, a pair of electromagnetically independent electromagnet windings included in said bridge, one on each side of said source of electricity and both energized thereby, and a signaling device rendered inert bythe passage of current through both of said Windings and adapted to be actuated by the passage of current through one of said windings, substantially as described.

40. The combination with a telephone line, of a charging source of electricity bridged between the limbs thereof, a pair of electromagnetic windings included in said bridge, one on each side of said source of electricity, and through which the whole ofthe energizing current is supplied to the telephone line during conversation, and a signaling device rendered. inert by the passage of current through both of said windings, and adapted assage of current through one of said win-d as described.

to be actuated by the ings, substantially 41. The combination with a telephone line,

of a charging source of electricity in a air of bridge between the limbs thereof, a electromagneticwindings included in said bridge, one on each side of said source of electricity and both included in the path of current supplied to the telephone line, the said electromagnetic windings furnishing impedance to said bridge across the' limbs of the telephone line, anda signaling device rendered inert by the-passage of'current through both of'said windings and adapted to be actuated by' the Jassage of current through one of said Win ings, substantially as described.

42. The combination with a telephone line, of a charging source of electricity bridged between the-limbs thereof, a pair of electromagnetically inde endent electromagnet' windings included in said bridge, one oneach side of said source oi electricity, and through which the whole of the energizing current is supplied to the telephone line during conversation, and a signaling device rendered inert by the passage of current through both of said windings and adapted to be actuated by the passage of current through one of said windings, substantially as described.

43. The combination with a telephone line, of a charging source of electricity bridged between thelimbsthereof, a pair of electromagnet windings included in said bridge, one'on each side of said source of electricity, the said electromagnetic windings furnishi'ng impedance to said bridge and furnishing the sole path. for the supply of energizing current to the telephone line for purposes of voice transmission, and a signaling device rendered inert by the passage of current through both of said windings and adapted to be actuated by the passage of current through one of said windings, substantially as described.

H. In a telephone system. the combinationwith subscribers lines having connection terminalsand line signalingdeviees at the central ollice, of a cord circuit to establish connections between the lines for conversation, said cord circuit having a strand -in each side of the talking circuit, n :ans

for inductively connecting, but conductively separating, the two ends of the cord circuit, means at the central oilicc' for supplying current to the lines for conversation, electromagnetically independent supervisory relay windings connected in series with said means for supplying current and between said cord strands and upon each side of said inductive means, a normally inoperative supervisory signal for each end of the cord circuit controlled respectively bythe said windings on the same side of the inductive means, the excitation of one of the said windings on each side of the inductive ineanscausing the operation of the cox-res sponding signal, and the simultaneous excitation of: the associated winding causing the said -signal to become inoperative. substantiallyus described.

45. In a telephone system, the combination with subscribers lines having connectionterminals and line signaling devicesatthe central office, of a cord circuit to establish connections between the lines for conversation, said cord circuit having a strand in each side of the talking circuit,

.means for inductively connecting and con- 'ductively separating the two ends of the cord circuit, means at the central ofiice for supplying current to the lines for conversation, supervisory. relay windings connected in serieswith said means for supplying current and between said cord strands and upon each side of the said inductive 'means nnd.

constituting the sole path for the supplyof current "to the telephone lines for conversation, a normally inoperative supervisory :signal for each end of the cord circuit controlled respectively by the said windings on the same s de of the inductive means,-the excitationof one of said windings oneach tide of the inductive means causingtlie operation of the corresponding signal, and the simultaneous, excitation of the associated winding causing sa'id'signal to. become noperative, substantially as described.

-16, In a telephone system, the combination with subscribers linesliaving connectionterminals and l ne signaling devices at the cent 'al ofiice, of a cord circuit to establish connections between the lines for con-,

versation, said cord circuit having a strand 'in each side of the'talking circuit, means for .vis'ory -relay windings;connected 'in series inductively connecting and conductively separating the two emls of the cord circuit, means at the central oflice for supplying current to the lines for conversation, superwith said means for supplying current and between said eordstrands and upon each side of the said inducti.e means, and'sup-.

. plying inductive 'rcsistance-between said cord strands.- a normally noperativesuperoperative.

visory signal for each end of the cord circuit controlled respectively by the said windings on the same side of the inductive means, the-excitation of-one-of said w ndings on each side of the inductive means causing the operation of the corresponding signal, and

the simultaneous excitation of the associated winding causing said signal to become iii- In a telephone system, the combination with SllbSClIl)l'$- lines having connectiou'tcrminals and line signaling devices at the central ottice, of a cord circuitto cstabl ish connections between the lines for conversation. said cord circuit having a strand in' each side of the talking circuit. means for inductively connecting and conducti vely separating the two ends of the .cord circuit,

means at the central otlice fonsupplying current to the lines for conversation. electromagnetically independent supervisory rclay windings connected in series with said means for supplying current. and between said cord strands and upon each side of thc said inductive means. and constituting the sole path for the supply '-.of talking tau-rent from said supply nieansto the associated si'ibscribci"s line. a normally inoperative supervisory signal for each end of the cord circuit controlled respectively by 'the said windings on the same side of the inductive iueans, the-excitatitfiu of oneuf the said windings on each side of the. inductive means causing the. operation ofthe .coi -resionding signal and the si|||iilt:\iieoiis cxcitation of the associated winding, causing the said signal tobecome inoperative, substantially as described.

. 48. In a telephone system, the combination with a telephone linc,of a pair of elec tromagnetically independent relay windings and a source of current supplyingcurrent through said relaywindings in a bridge be-- tween the two limbs of the talking circuit thereof, a switch at the substation and a switch at the central station for controlling the circuits through said relay windings,

ergization of said relay windings, substantially as described.

49. In a telephone system, the combina tioii with 'a telephone line, of a source of current and a 'pair of ,relay' windings bridgedbetween the two limbs of the talk-- ing circuit thereof, and through which all of the current-is supplied to the telephone. line during conversation, a. switch at the substation and a switch at the central station for controlling thecircuits through saidrelay windings, and a signal controlled by the conjoint energization of said relay windings, substantially as described.

50. In a telephone system, the combinintion with a telephone line, of a pair of relay windings constituting an inductive resistance and a source of current delivering current through said relay windings in a bridge.

between'tl etwo limbs of the talking circuit thereof, a switch at the; substation and a switch at the centralstation for controll ng the circuits through said relay windings, and a signal controlled by the con omt energization of Stlltl relay windings, substantially as described.

51. In a telephone system.the'con bina tion with a telephone line, of a source of and a signal controlled by the conjoint encurrentand an electromagnetic winding bridged between the two limbs of the talking circuit thereof. a second electromagnetic winding connected in a circuit including'a portion of one side of the talking circuit, and means for energizing it; the current for conversational' purposes being supplied to said line .wholly through said electromag-- pho'nelinc .frcc from permanent grounds Ul|i ltl0 the central other. of a cord circuit. a

charging current source, a third conductor,

a pair-of relay windings associated with the cord'cii'cuit,.one of said windings being cncrgized over the telephone line and the other over a portion of the talking circuit, aml the third conductor, the said relay windings constituting the sole 'path for the 1Q i concise supply of current to the telephone line dur- 7 ing its connectionf for' conversation,"\and a signal controlled by the conjoint action of- 'said relay windings,substantially as 'de- 'SCIib6d. 4

53. The,.co1nb1nat1on w1th"a telephone 'l1ne,.of a charging source of electricity anda pair of electromagnetically independent relay windings connected 'in a bridge be-" tween the limbs of the talking circuit there-- of and conveying current from, said charg-.

ing source-to said telephone line, a switch at the central station for controlling 'the circuit through said'relay windings, and, a signal adapted to be controlled by' the conjoint v action of said windings, substantiallyas described; 54. In a telephone. system, the combination with a cord circuithavinghro talking strands, of a source (if-electricity and a pair of relaywindings adapted to be bridged between the two talking strands of the cord circuit, a telephone line connected-withsaid cord circuitand free from anysource of current supply other than that through the said relay -windings ,and cord circuit strands, aswitch at the central station for controlling the circuit through said relay windings, and ,a signal adapted-to be conoffice, a pair of electromagnetically independent electromagnet windings through trolled by the-conjoint action of said windings, substantially as descri bed.'

55, The' combination W1ill'l a. telephone line, of a charging source ofelectricity, and

a pair of relay windings connected iii a bridge between the *limbs of the talking circuit thereof, the said relay windings furnishing inductiveresistance to the, bridge circuit and supplying talking current to t telephone line, aswitch at'the' central Sta-- tion for controlling the circuit through said relay windings, and 'asignal adapted to be controlled by the' conjoint action of said windings, substantially as described.

56. In a telephonei exchange system, a

plurality. of bi -metallic telephone lines. ex tendingfromsubstations to a central ofiice,

a pair of link'conductors at the central office for connecting the two ,limbs .of'one line "with the two limbs of another line for conversation, a source of currentat the central which current is fed from said source through said link conductorsto supply'current for conversational purposes to a tele--' phone line, and signaling. mechan sm actw' ated by said electromagnetwindings. s

' 57. In a telephone 1 exchange system, a

telephone :line extending from-a substation tromagnet windingsthrough w 'ch current.

to a central ofiice, a pair of link conductors at the central ,oflice for connectingsaid line with another for conversation, a -source of current at the central oflice,-a air of elecis fed from said source through said link conductors to sa d telephone line, the said electromagnet windings being relatively disposed to -1ntroduce impedance into the circuit through wh 1ch current 1s fed to the.

telephone line, and a clearing out device actuated by the magnetic effects of said electrolnagn'et windings. v 58. In 'a telephone exchange system, a

telephone-line extending'froln a substation to a central ofhce, a source of current at the central ofiice, a pair of electromagnetically I independent electromagnet windings constit-uting the sole path for thc'supply. of talki'ng'current to said tclephone hne, and signaling mechanism adapted to assume either .of two' conditions as determined solely by themag'netic efi'ects of said electroinagnet windin s. s V

59. I n a telephone exchange system, a

telephone line extending from a. substation ated solely bythe magnetic etfect of the associated electromagnet winding.

60. In a telephone exchange system, a telephone line extendmg from a substation to a .central ofiice, a source of current at the central oflice,'a pair of electromagnet windings constituting the sole path for the supply of talking current' to said telephone line, a

Separate armature for each of said electromagnet windings, each armature being controlled solely by the magnetic effect of the associated elect-ronuagnet w'indin fand signaling mechanism jointly control ed by said armatures- -,61. In a telephone exchan system, a

- telephone line'cxtendin'g from a substation to the central ofiice, a source of current at the: central office, a pair of electromagnet windings constituting-the sole' path for the supply of talking current to said telephone line, an armature responsive to the magnetic effect of each electromagnet winding, butunresponsive to the magnetic effect of the other electromagnet winding.

'62. In a telephone system, in combination,

a .calling teleplhone hue and 0. called telephone line eac extending from a substation to a central ofiice, a'spring-jack for each lme,

a cord circuit having an answering plug and a calling plug connecting sa1d-ln1es,a pair of relays. and a-sourcc of current-1n a bridgeacross the talking circuit ofthe called line, one of said relays being actuated sollyzby current flowing over a circuit closed by the insertion of the calling plug i-iito the jack-- of the called line, and the otheractuated vupon the response'of' the called subscriber,

I said conductors, one bridge on either side ofand a signal controlled the joint actionofsaid relays. V

'63. Ina telephone system, in combination, a pair of"voice-cui'rcntconductors, a condenser in each conductor, tworpa-irs' of relays and a source of currentin bridge between said condensers, a central'ofiic'e switch in the circuit of one relay of each pair, a substation "switch in the circuit of the other relay of 'eachlpair, and signalin 'inechanism controlled by the magneticetiects'of-said relays. In a telephone system, in combination,

I a pair of voice-'current conductors. a condenser in each conductor. two pairs of electromagnets and a source'of current in bridge between said conductors, a central office .switch in the circuit of one elect-i'oinagnet of each pair, a substation switch in th'e circuit of-the other electromagnet of'each-pair, and switching mechanism controlled by said electromiignets. v r I i 65.' In a telephone system. in combination, a pair of. voice-currentconductors. a condenser in each conductor. a pair of electromagnet windings and a source of current in and asource of. current in a bridge between said conductors. one pair on each side of said I condensers. contacts of an illl$\\'8l'1ll plug in a bridge between said conductors. a central office switchin the circuit of one 'electroanagnetwinding. a substation switch in. the 3 circuit of the other electromagnet winding.

and switching apparatus controlled by sa d electroinagiiet windings.

66. In a telephone exchange system, the combination of a calling telephone lin'e and a calledtelephone .linc; each extending from a substation to a central ofiice. a cord circuit comprising a. pair of voice-current conductors for connecting'said lines for conversation. a condenser'in each voice-current conductor, two pairs of electromagnet windings the. circuit of oneelectroinagnet winding of one pair, a calling substation switch in the circuit of the other electromagnet winding of said pair, contacts of a calling plug in the circuit of onecelectroniagnet winding of the otherpair, it called substation switch n the circuit of the other 'elcctromagnet winding of the second pair. and switching mechanism controlled by each electrom'agnet winding.

source, a third conductor, twopairs of re lays at the central ofiice,- onerelav of one pair being energized over the calling telephone line, and theother relav ofsaid pair being energized over a portion of the talking circuit of the calling line and said third conductor, and one relay of the other pair beingenergized over the called tele )hone v line; and the other relay of said seconc pair being energized orer a'poi'tion of the talking circuit" of. the called line and said third I conductor.

68. In; a telephonesystem.a calling and a called subscribers"sta tion. a pair otvoicecurrent conductors connecting said stations, lllCltlCiZlVE means included in eacli'of said voice-current 'conductors,' a pair of relays and a charging currentgsource in, a bridge 1 across the conductors leading from the called station, an operators switch and a subscriber'sswitch for controlling said'i'elay, and a signal ointly controlled by said relays.

GtlQThe combination with a pair of telcphone lines, of an inductive device through which the same are adapted tobe united'tor conyersatioira charging S;|ll1(?&,0f electricity 1 and a pair of relays adapted to be bridged between the two limbs of each ofsaid lines. one pair of relays being individual to one of said lines and the other pair beingindiiiidual tothe other line, switches at-the substations and at the central station for controlling the circuit through saidrelavs and a an v 3 signal controlled by the conjoint. action of each pair of relays, substantially a'sdescribed. 1

70. T he combination with telephone lines extending from subscribersstations ;to an OXLlii11lgO.'0f a cord circuit at thc'exchangc provided with two strands for formingconnections between two telephone llll:=.1tl pa rion of relays corresponding to each end of tl ef cord circuit and included in bridge thereof. a source of current tor inclusion lllcircuit with each of Silltl pairs of relays, a super- ,visory ,signalHforeach pair ot. relays a'nd p jointly controlled thereby, switching apparatus for controlling the operationof the relays. and. a condenser includcdin each cord strand between the connections of the relays therewith.

T1. The combination with telephone lines extending from substations to jacks at an exchange, of a cord circuit at the exchange provided with two strands for forn'iing connections-between subscribers lines. a pair of relays corresponding to each 'end of thc cord circuit and included in bridge thereof, a source of current for energizing said relays, a supervisory signal-for each pair of relaysand jointly controlled thereby 5 switching mechanism atthe substations for controlling the operation of one ofeach pair of relays,

means including a jack and a'cord circuitplug inserted in the ack, whereby a closed circuitis established through the remaining relay of each'pair which is independent. of

the operative' position of the substation ap- 1' paratusg. and a 4 condenser ,included in each cord strand between 'theconnectionsof the relays therewith. 1 q

72. In a telephones stem; thefconibma-f tion with a' telephcne ine ofbranchcon 73. Ina telephone system, the coiilbina- "ti'on with a teleph e of a Source bf rent normally connected in a bridge ofthe limbs of said line at the central office, a cord circuit having two voice-current conductorsadapted to be connected vith'the conductors of;the lino, cut-ofi' contacts for the-lineadapted to sever the circuit of said normal bridge when the cord is connected .wlththe "line, a pair of relays'for'the.cortlcircuit, a

third'conducton om of said relays being actuatedover the telephone line and the other over a-portion of the talkingcircuit'and said- :third conductor, and a 51 the conjoint action of sai relays? v 74. In aiteleplione 3 system, the combination with a telephone line, of a line signaling device and a battery in circuit withthe limbs,

of the line, a cord circuit forconnection with the line, means operative upon the connedtion of thecord withthe line for opening the circuit of saidbattery and signaling device,- 3

apair of-relays bridged acrossthe cord circuit and adapted'to furnishthe path-for. cur- 1 conjoint-action'of sai .relays.

rent to' the limbs ofthe'line-for transmitten energization, .anda si al'cont rollfed rent and-a signal controlling device nor-- mally connected lgctween theylimbs of;-the' telephone line a cord circuit and plug r for fator and. efsi connection with the 1' line, means. operative upon the connection of; the

e y Wigs,

- ,actioniof relays g w Mensa-. bee;

al'oont'mnediby said line signal; substantially as described,

atcdwith the :line atithe central Mike, a pair of link conductors at the central office for connect-in'gthetwo limbs of said line with another for-- -conversation, a source =otcurrent at the -.-centr'al, ofiice, .a a pair of electromagnetically independent electromagnet windin gs through electromagnetwindings and means. for re-- tiring. the line ."signal u on .theeonnection of the links conductors with the limbs of the telephone line."

77. The combination with a metallic tel'e phone-l-m, of a line signal for-said line, an' operators plug anda cord circuit for con.v

'nection' with said line, a source of currentand a panof'relays 1n a bridge-acrosssald cordcircuit' a third conductor connected 'with'lone poi lays being adapt'ed 'tobe operated over the metallic hnegwhe'n the subscribers telephone is useg' and the other} to be operated by current supplied from said source over a part, of the line and' 'said'third conductor when" the subscribers' telephone 'lS notin use and the operators plug is connect with the line, and --means.flwhereby the connection of the operators plugjwit'h the line retires '7 8. Thelcor'nbination with a telephone line, of a cord circuit for connectiontherewith, a. source of. el'ectr1city and a pair of. relays permanently e'bx'fid'ge'd between the 'limbs 0f the talkin -circu1t of said cord circuit, a

switch-latt til-substation and a switchjat the central stationf for controlling :the l circuit through vsaid relays, and, ai si 'te becontrolled by the .conjomt action of f a R Y -K 1 '79, The bombin'fatitin a metallictelephone ;.linef fr ee';}from -permanent' grounds I I ;i r w 'foutside the-ccntfal oflice;ofaJcharging cur- 75.1111 'agtelephone- -system-,-"the'*comb1nation with atelephon'eline, of a source of cur-11' gnal adapted rentF's'ourc'e; a third" conductor,- a pa r of relays at the'f'central ofli'ce -ealg'zh permanently connected withi-seidsource -.one of; said ,re-

lays 'beingenergized over the :tele' 'ho'neline andthe'other over-ajportion: of t e talking "circuit andthethirdconductor. plug wlthgthe 'line for opening tlici circuit 0f- :saidj;sig'nal controlling device and entirely severing the} I vnormal'fconfiectionofflsaidsource' fromxthe: limbsof. the line, a-pai'r'orrela s int-bridge of-thecortl circui -one ofsai I actuated ovef ltlie 'ineand beiv I V ,control of the subscrlbergfand"theother o r a port o'nfof' the talking circuit" and" uncler: .the: control of the central office ope'i conttolled by. the conjoint 7 a '80; The combination with ainetallic telephone-li'ne; of one rators plug 'and'alcoir} airo relays-permanently- Bridged across said cord 1; circuitf ajthird conductor connected with one and t T pole-0 said""source,'.one' of said relays being 4 er I,

adapted to'be operated .o'ver the metallic line when the-:subscribers telephone is in use andgthe'other to be operated over a part of the -line'and said third conductor when the subscribers";.line is noti-in' use and the operators'plugis connected with the line.

unds' v current-is fed from said sourcethrou h 'said'link conductors to-supplycu'rrent or conversational purposesto said. telephone fline, signaling mechanism actuated by. said e of said source',- one of said -re-- when rent source, a third conductor, a-pair of relaysa't'the central oflice, one of said role 8 being energized by current supplied sole y from said charging current source-over. the telephone-line, and the other being energized I by current supplied, solely from the same chargin current source over a portion of thetalking circuit and the third conductor.

82. In a'telephone. system, the combination Vltl1 a telephonenline, of a source of electricity at the-central ofiice, an operators plug, and a pair ofrelays permanently connected with said source of electricity and associated with said plug, one of said relays being energized from the said source of electricity'as long as the said-operators plug is connected with said line and over a path having a part coincident with the talking circuit, and theother relay being energized. as, long as the said operators plug 1s connected with the said line and when the subscribers telephone is in use, and a signal as- I sociated with said pair of relays, the circuit of said signal being established by the operation of the first of said relays, and said signal -bein rendered inoperative by the operation 0 the second of said relays.

83.--In a telephone system, an operators 'cordcircuit, 'a pairof relays permanently connected together and each operated over circuits including portions of-the talking circuit, and a supervisory signal havingits circuitcontrolled by the contacts of both said relays, one of saidrelays being adapted to normally close thecircuit and to be energized over the telephone line when the line is in use, whereby thesignal is at-that time rendered inert and the other'relay being adapted to normally open the circuit, whereby when the cord circuit is not connected with the line the signalis inert,'and when connected with. a line not in use the. signal is displayed. In witness whereof, I hereunto subscribe my name this eleventh day of February Copies ofthis patent may be obtained for f ve-cents each, by addressing the coinmlsstone'r of Patents,

Washin'gtom'l). 0; i 

